k0ua
Epic Contributor
Hey it is a start, and you made something useful.. you should be proud... heck I am.:thumbsup:
James K0UA
Thoughts on this used welder?
- Thread starter joshuabardwell
- Start date
Hey it is a start, and you made something useful.. you should be proud... heck I am.:thumbsup:
James K0UA
Shield Arc
Super Member
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joshuabardwell
Elite Member
I think I would have done better with a smaller-diameter rod and if I had removed all of the plastic from the hooks, instead of just the plastic where I was going to weld (for better grounding). I think with a smaller diameter rod, I could have kind of worked around the base of the screw a little. As it was, I just sort of globbed on from both sides.
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joshuabardwell
Elite Member
Well, I gave it a go with the old IR thermometer, and nothing really useful came from it. I mean, some parts were warmer than other parts, over maybe a ten degree range, but nothing jumped out. I am kind of fed up and I think I am just going to focus on AC practice for a while.
I can't decide if the next step in troubleshooting the DC, when I get around to it, should be to start pulling the DC side apart and looking for corroded connections or heat marks to indicate a bad connection, or whether I should roll the dice that, if anything has failed, it's probably the diodes (no matter what the diode test says) and just buy four new diodes and cross my fingers. I could always use this as an excuse to buy an amp clamp and track through the circuit path looking for where the current flow drops out, but that'd nearly be as expensive as just buying the new diodes.
Or, heaven forbid, take it to a welding shop and see what it will cost to get it fixed. :shocked:
CNC Dan
Veteran Member
I would disconnect, clean, re-connect, any and all terminals in the DC section. If no joy, then go for the diodes.joshuabardwell said:
Note: sometimes diodes in welders are of two kinds. One has the cathode at the stud, the other has the anode at the stud. You will need two of each. Save some $ and get them from a electronics supply, or surplus place. Just needs to meet minimum volts and amps. More is better. And a good thermal connection to the heat sink they are bolted to is important too.
terraformer
Silver Member
When I weld with my Miller 225 thunderbolt on DC and use 1/8" 6011 I have it turned up all the way, 140A.
I have a bunch of 7014 in 3/32" and they weld well at about 90 amps.
I have a bunch of 7014 in 3/32" and they weld well at about 90 amps.
CNC Dan
Veteran Member
Wait a sec. Wasn't there a fifth loose diode or something?
Could someone else have replaced the diodes in the wrong way(lookup bridge rectifier)?
Can you put a load on the welders DC output (two car headlights in series?), then measure the volts across each connection. A good connection should read near 0 volts.
Don't forget the lead sockets.
Could someone else have replaced the diodes in the wrong way(lookup bridge rectifier)?
Can you put a load on the welders DC output (two car headlights in series?), then measure the volts across each connection. A good connection should read near 0 volts.
Don't forget the lead sockets.
OP
joshuabardwell
Elite Member
Not sure what you're getting at, Dan. I have used a 12 volt battery and a tail-light along with my multimeter's diode test function to test the individual diodes. They checked out good.
For someone to have replaced the diode the wrong way, they would have had to order a wrong-polarity diode and replace it. There's only one way to put in the type of diodes that are in here. They have a barrel that bolts to the aluminum plate and a lead that is soldered to a piece of wire. You couldn't reverse them if you wanted to. But, honestly, to my eye, it all looks original. The solder on the diode leads looks factory to me, and all the diodes are the same model number and match the model number that should have shipped with the welder. I suppose it's possible that someone disassembled it and put it back in the wrong order. Not sure how I would track that down, as I am not confident in my ability to translate a wiring diagram to real life. At least not a circuit this complex.
There isn't a fifth diode that I can see. Four diodes, a choke, and a capacitor.
You're saying to crank up the welder and put a load between the work clamp and the stinger, then measure voltage where exactly?
CNC Dan
Veteran Member
OK my mistake.joshuabardwell said:
Any and all connections. Set VOM to read volts, and apply probes to things that _should_ be in good contact with each other. If the connection is good, the meter should show near zero volts. I'm thinking bolt/screw connections.
Diode to heatsink.
Heatsink to choke.
Choke to socket.
Socket to cable.
Diode in / diode out.
Choke in / choke out.
You're losing power somewhere between the AC output from the main transformer and the output of the DC sockets. I'm starting to think it's got to be a poor connection.
OP
joshuabardwell
Elite Member
I think I see what you're getting at. But will the loss in power translate to a drop in voltage? Or would I need something that measures current, like an amp clamp? Current = Volts / Resistance, right? So if resistance goes up somewhere in the circuit, current will drop while voltage will remain constant. No?